No, I don’t think Google is trying to be evil. Moreover, there are lots of other ways to broadcast steganographically encrypted messages on the web, such as posting comments on unmoderated blogs. But it’s interesting that this is the first “useful” application I’ve seen proposed for SearchWiki.

Many attempts to read the hidden messages can be discovered by analyzing the search patterns of users, looking for users that regularly repeat the same search queries. By analyzing the results of those queries, it might be possible to get the messages prior to the persons it was intended to reach.

Yes, but that is at best looking for needles in a haystack. And I believe there are some computational complexity results on the relative difficulty of obfuscating vs. detecting obfuscation that strongly favor the obfuscators. Even in a simplified model of stenography, I have to imagine that the detection problem is at least NP-hard.